So today I put a Big Gun exhaust on my Honda 400ex and after I was done it wouldn’t start. It started for like 10 seconds then stops it did this 1 or 2 times. I was thinking it’s because i didn’t jet my carb yet. Could someone help me and tell me if it’s prob just me not having the jets in

 

Don't know the EX model but putting on choke has the affect of bigger jets, so it should run on choke, or part choke, even if it won't run without any.